Self-propelled rollers, in which the front and rear drum frames are connected to each other by means of a center pivot, and which are steered by means of an hydraulically operated steering cylinder, have been previously known. These arrangements allow the drums to track, but they are expensive to manufacture and they occupy much space, so that a longer roller wheel base with a resultant larger turning radius is necessary.
Rollers are also known which have a pair of drum frames, pivoted on a common chassis, which frames are swiveled with the aid of hydraulically operated cylinders connected to each of the frames. The drawbacks of this design, however, are the difficulty of achieving simultaneity in the swiveling motion of the drum frames, and the difficulty of achieving an equal amount of lock or an equal degree of swivel on both drum frames.
On articulated rollers, the center of gravity of the roller moves laterally when the roller changes direction. There is thus a danger of the roller tipping over, particularly when making sharp turns. Furthermore, this danger becomes greater with increased roller speed due to the effect of centrifugal force.